Are Bioidentical Hormones Safe?

Menopausal women are increasingly using them instead of hormone replacement therapy

It's important to note that there are several FDA-approved hormones that are also exactly the same — molecule for molecule — as natural hormones. Examples include Estrace pills, Estrasorb topical cream and the Alora patch. "The term 'bioidentical' is really a misnomer," says Nanette Santoro, M.D., chair of the department of obstetrics and gynecology at the University of Colorado in Denver and a spokesperson for the Endocrine Society. "The real issue is pharmacy-compounded hormones versus those that have been FDA approved."

Compounded hormones have been around for decades, but interest in them surged in 2002 after researchers published the startling results of the Women's Health Initiative. The study of more than 16,600 postmenopausal women found that taking a combination of estrogen and progestin increased the risk of breast cancer by about 25 percent. Surprisingly, the combination also more than doubled the risk of heart disease in the first two years. "The WHI made some doctors as well as many patients a little disenchanted and distrustful of standard hormones," Stuenkel says.

New study links hormones, breast cancer

As researchers continued to follow the women involved in the WHI, the news only got worse. A study published in the Journal of the American Medical Association in October 2010 found that when women taking Prempro developed breast cancer, the cancer was likely to be unusually aggressive. On the whole, women on the hormones were about twice as likely as other women to die of breast cancer within eight years. "Most of the deaths occurred more than five years after starting hormone treatments," says lead researcher Rowan Chlebowski, M.D., a medical oncologist with the Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center. "We could be seeing a lot more of these [deaths] as time moves forward."

Doctors' advice

Although such results are alarming, they shouldn't change the current approach for hormone therapy, says study coauthor JoAnn Manson, M.D., professor of medicine at Harvard Medical School and chief of preventive medicine at Brigham and Women's Hospital in Boston. Manson is also the president-elect of the North American Menopause Society.

"I've been getting a lot of e-mails from patients wondering how this study applies to them," she says. As before, she says, women should take combination hormone therapy only if they have moderate-to-severe menopausal symptoms. And they should get the lowest doses for the shortest time possible. She reassures women taking estrogen by itself — a common approach for women who have had hysterectomies — that estrogen alone doesn't seem to promote breast cancer.

When patients ask about bioidentical hormones, Manson tells them they're in uncharted territory. Although there's some early evidence that the micronized progesterone Prometrium — a bioidentical hormone — may be less likely than Provera to cause breast cancer, Manson says she's still "working from the assumption that bioidentical hormones are just as dangerous until proven otherwise. And the proof just isn't there."

Promoters of compounded hormones often claim that their treatments carry none of the risks of Premarin and Provera. John Woodward, M.D., a board-certified ob-gyn practicing in Dallas, has been giving his patients compounded hormones — most often estradiol pellets injected under the skin — since the early 1970s. On his website, Woodward points to unpublished tests at the respected Cooper Clinic in Dallas in the 1990s showing that his patients tended to have stronger bones and cleaner arteries than other women of the same age.